Issue 30

L. Náhlík et alii, Frattura ed Integrità Strutturale, 30 (2014) 55-61; DOI: 10.3221/IGF-ESIS.30.08

Focussed on: Fracture and Structural Integrity related Issues

Critical applied stresses for a crack initiation from a sharp V-notch

L. Náhlík, P. Hutař Institute of Physics of Materials, Academy of Sciences of the Czech Republic, Žižkova 22, 616 62 Brno, Czech Republic nahlik@ipm.cz, hutar@ipm.cz K. Štegnerová Institute of Physics of Materials, Academy of Sciences of the Czech Republic Faculty of Mechanical Engineering, Brno University of Technology, Brno, Czech Republic stegnerova@ipm.cz A BSTRACT . The aim of the paper is to estimate a value of the critical applied stress for a crack initiation from a sharp V-notch tip. The classical approach of the linear elastic fracture mechanics (LELM) was generalized, because the stress singularity exponent differs from 0.5 in the studied case. The value of the stress singularity exponent depends on the V-notch opening angle. The finite element method was used for a determination of stress distribution in the vicinity of the sharp V-notch tip and for the estimation of the generalized stress intensity factor depending on the V-notch opening angle. Critical value of the generalized stress intensity factor was obtained using stability criteria based on the opening stress component averaged over a critical distance d from the V-notch tip and generalized strain energy density factor. Calculated values of the critical applied stresses were compared with experimental data from the literature and applicability of the LEFM concept is discussed. K EYWORDS . Crack initiation; V-notch; critical stress; strain energy density factor; generalized linear elastic fracture mechanics; fracture criteria. any of material discontinuities can be treated as notches which causes high stress and strain concentration near the notch root. Due to nature of notch, which represents stress concentrator, the crack can initiate in the notch root and consequently its existence can lead to the failure of the whole structure. Due to this reason, the notch behavior and crack initiation from the notch are still in the interest of researchers and engineers. The problem of stress singularities at angular corners was firstly solved by Williams [1, 2] and others [3, 4]. Kotousov followed up Williams’ works and studied the corner singularities for a sector plate within the first-order plate theory by using stress resultant and displacement functions [5-7] and adapting the eigenfunction expansion approach of Williams [1]. However, the specificity of the singular stress field in the vicinity of V-notch is studied from experimental side as well, see e.g. [8, 9]. In the last five years occur works pointing out on the complexity of the stress field around the notch tip and influence of out-of-plane singularity caused in the so-called vertex point [10-14]. The knowledge of the M I NTRODUCTION

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